Whenever i insert a obj file, it's placed somewhere and idk how to get it normal
As far as I know, OBJs are imported relative to their own coordinate systems. So try to set it to (0,0,0) in its own environment before exporting.

Another aproach would be to hit Shift+S > Cursor To Center, and after that Shift+S > Selection To Cursor – after that, your object is centered.